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Zoltan Toth, Steve Albers, and Yuanfu Xie

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Zoltan Toth, Mark Tew, Daniel Birkenheuer, Steve Albers, Yuanfu Xie, and Brian Motta

The Local Analysis and Prediction System (LAPS) is a highly portable, computationally efficient numerical weather prediction (NWP) data assimilation and nowcasting system. The first version of LAPS was developed in the late 1980s and early 1990s (Albers et al. 1996). LAPS offers very frequently updated (15–30 min), very finescale (1–3 km) analyses assimilating most locally available observations, and ensuing forecast products with low latency, using versions of the Weather Research Forecast (WRF) or other models. The primary use of LAPS is in situational awareness and very short range forecasting [warn on forecasting (WOF)].

Within the National Oceanic and Atmospheric Administration

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Hongli Jiang, Steve Albers, Yuanfu Xie, Zoltan Toth, Isidora Jankov, Michael Scotten, Joseph Picca, Greg Stumpf, Darrel Kingfield, Daniel Birkenheuer, and Brian Motta


The accurate and timely depiction of the state of the atmosphere on multiple scales is critical to enhance forecaster situational awareness and to initialize very short-range numerical forecasts in support of nowcasting activities. The Local Analysis and Prediction System (LAPS) of the Earth System Research Laboratory (ESRL)/Global Systems Division (GSD) is a numerical data assimilation and forecast system designed to serve such very finescale applications. LAPS is used operationally by more than 20 national and international agencies, including the NWS, where it has been operational in the Advanced Weather Interactive Processing System (AWIPS) since 1995.

Using computationally efficient and scientifically advanced methods such as a multigrid technique that adds observational information on progressively finer scales in successive iterations, GSD recently introduced a new, variational version of LAPS (vLAPS). Surface and 3D analyses generated by vLAPS were tested in the Hazardous Weather Testbed (HWT) to gauge their utility in both situational awareness and nowcasting applications. On a number of occasions, forecasters found that the vLAPS analyses and ensuing very short-range forecasts provided useful guidance for the development of severe weather events, including tornadic storms, while in some other cases the guidance was less sufficient.

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